What movie design choice did you think didn't match up to your imagination/expectations?

I doubt it was motivated. This kind of background character recast is common and when it came to movie 6 we needed someone who could play onscreen with the trio. Maybe Jessie Cave was the best they auditioned (and her portrayal was pretty singular, leaving more of an impression than Rowling ever did with the character).

That said, I wish to God they could have enacted the same manner of recasting on Ginny. Bonnie Wright is a wooden board in the role. She has no charisma as Ginny and no chemistry with Radcliffe.